Product dispensers may take many different shapes and sizes. Each dispenser generally requires some sort of product illumination and/or signage illumination. Due to the increased lifetime and decreased power usage, light emitting diode (“LED”) lighting is becoming common in many lighting applications. Typical LEDs used for illumination in a product dispenser setting may range from 0.5 to 3 watts and 25 to 70 lumens per watt. Such LEDs may typically be rated to operate for 40,000 to 50,000 hours before failure. Unlike many light sources, where failure is defined as a point in time at which no output is being produced, LED failure is typically defined as a point in time where the luminous output is less than 70% of the original output of the LED.
While the failure mode in LEDs is more desirable than the failure mode of other light sources, a problem remains. For example, many product vending machines employ LEDs to illuminate product selections available for purchase. When a vending machine containing a “young” LED array is located next to a vending machine with an “aged” LED array (one that has not failed, but has degraded and produces less output than originally desired), the significant difference in luminous output is readily apparent to a potential consumer due to the light degradation that has occurred in the “aged” LED array.
A dimly lit dispenser or a dispenser with a degraded lighting source may give a consumer at least the perception that the products therein are not adequately maintained. Resultantly, potential consumers will tend to make a purchase from the vending machine with the “younger” LED array as the appearance is more visually appealing and catches the eye of the consumer. These LED issues generally need to be addressed in the context of adequate product marketing, i.e., the dispenser and the products therein should be properly illuminated so as to be visually appealing and catch the eye of the consumer.
There is a desire, therefore, for an improved LED powering scheme which maintains consistent luminous output for the rated life of the LED. This improved LED powering scheme should provide for uniform appearance of LEDs over their practical lifetime.